Deposition of Co islands on Cu(111) and Cu–Al(111): A comparative study from DFT calculations

Abstract

The growth behaviors, stability and magnetic moments of Co islands on Cu(111) surface and Cu–Al(111) alloy surface were compared by means of Density Functional Theory calculations. Similar to the case of Pb-precovered Cu(111), it was found that the diffusivity of Co adatom on Cu–Al(111) was lower than that on Cu(111), which could suppress the agglomeration of Co atoms on Cu–Al(111). Such behaviors could be explained by the different electronic structures of surface atoms of Cu(111) and Cu–Al(111). Co adatoms deposited on one monolayer Co island descending a Co edge step to substrate terrace via push-out/exchange mechanism is more favored than direct hopping on both surfaces, and push-out/exchange descent is more favorable on Cu–Al(111) than Cu(111) with similar “Schwoebel-Ehrlich” barrier and larger exothermic reaction energy. Island formation energies calculated suggest layer-by-layer growth mode is more favored for Co islands deposited on Cu–Al(111) covered with Co films than that on Cu(111). In agreement with experiments, layer-by-layer growth is identified for Co islands on Cu–Al(111), suggesting perfect wetting of Cu–Al(111) by Co. Our calculations show Al impurities in Cu(111) enhance the stability and magnetic moments of Co islands, which may shed light on Co/Cu–Al(111) being potential applications in magnetic hyperthermia treatments.